There is more to glass than meets the eye. Literally, thousands of different types of glass are built off the basic molecule of SiO2. Each has unique properties and performance characteristics. Glass can be coated with chemical films, silvered (mirror), heat or chemically tempered (strengthened), be thicker or thinner, clear or tinted…on and on…
It’s hard to look anywhere and not see glass in some form or another. Ubiquitous now, in ancient times glass was rarer (and more valuable) than gold. Found near volcanoes that had at one time spewed lava consisting mainly of sandstone, and where that lava flowed into a body of cold water, the molten sand mixture congealed as a super thick and viscous liquid rather than solidify into rocks or quartz crystals. Very old windows are thicker at their bottoms- they flowed.
A chunk of this stuff (called basalt) could be smashed against a rock, yielding sharp as razor shards, useful for carving, tool making, spear points, and even scalpels (glass scalpels are still in use today…very sharp).
During the Italian Renaissance in the 1300’s, the art of glass making really took off (Italy still leads the world in glass making, glass working machinery, and glass art). By the dawn of the Industrial Revolution, glass was firmly established as the important building component it is today.
Molten glass can be cooled quickly to form annealed glass (the super viscous liquid form) or slowly cooled, yielding tempered glass which is chemically similar to quartz. Tempered glass is about four times stronger than annealed glass, but when really stressed or impacted, explodes into a thousand little crystals, instead of sharp and dangerous shards as regular annealed glass does. It makes a mess, but it’s considered a safety glass because the little glass crystals won’t cut you.
The machines that produce glass run 24/7, usually for 15 or 20 years and can be 1.25 miles long. The whole process is a marvel of modern engineering and with human ingenuity, is always advancing.